<template>
  <div>
    <span>全选:</span>
    <input type="checkbox" v-model="isAll"/>
    <button @click="fs">反选</button>
    <ul v-for="(item,ind) in arr" :key="ind">
      <li>
        <input type="checkbox" v-model="item.c"/>
        <span>{{ item.name }}</span>
      </li>
    </ul>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "猪八戒",
          c: false,
        },
        {
          name: "孙悟空",
          c: false,
        },
        {
          name: "唐僧",
          c: false,
        },
        {
          name: "白龙马",
          c: false,
        },
      ],
    };
  },
methods:{ 
fs(){
  this.arr.forEach(item => item.c = !item.c)
}
},
  computed:{
      isAll:{
        // val是监听到的isAll的值
        set(val){
          // console.log(val);
          // 将变化的val赋值给每一个小li的c
          this.arr.forEach(item => item.c = val)
        },
        get(){
          return this.arr.every(item => item.c === true)
        }
      }
  }
};
</script>

<style>
body{
  padding: 30px;
}
</style>